Les,

Let me tell you my philosophy on stove fuels: If it burns good, it is good.

Seriously. If you're getting a good flame, then I'd say that's a good fuel. It's certainly not going to hurt anything unless you see charring, warping, soot build up, or something like that.

Important point at this juncture: You were using a 70% solution. Normally, high concentration isopropanol is a smokey mess that doesn't burn cleanly. So, important tip: If you're going to use isopropanol as a fuel, it must be a lesser concentration.

HJ